Coded range-signal responsive system



July 4, 1950 w. c. MOORE 2,514,285

CODED RANGE-SIGNAL RESPONSIVE SYSTEM Filed July 24, 1944 3 Sheets-Sheet 1 0 RANGE o SIGNAL INVENTOR. ,WILLIAM CULLEN MOORE ATTORNEYS July 4, 1950 w. 'c. MOORE consn RANGE-SIGNAL RESPONSIVE SYSTEM 3 Sheets-Sheet 2 Filed July 24, 1944 INVENTOR. WILLIAM CULLEN MOORE flfi-ddafiflfaa m OE ATTORNEYS W. C. MOORE CODED RANGE-SIGNAL RESPONSIVE SYSTEM July 4, 1950 3 Sheets-Sheet 3 Filed July 24, 1944 WILLIAM CULLEN MOORE Wanda/fwd,

ATTORNEYS Patented July 4, 1950 SATES CODED RANGE-SIGNAL RESPONSIVE SYSTEM William Cullen Moore, Chicago, 111., assignor to Motorola, Inc., a corporation of Illinois 25 Claims.

This invention relates to coded range-signal responsive systems for aircraft and more particularly to such systems by means of which there may be derived an effect representative of the quadrant in which the aircraft is flying, such effect being either a visual indication or an electrical efiect utilizable for navigational control purposes.

It is well-known that one of the basic radionavigational aids to commercial aviation is the radio range or coded radio-range signalling system. Briefly, this system comprises a series of transmitters spaced at intervals along an air route, eachsending out a given pulse-coded, tonemodulated wave signal in opposite quadrants and a differently coded signal in the intervening quadrants, the division between the quadrants lying along the course of the route. The aircraft pilot, by listening to the received code Signals, can determine the quadrant in which he is flying and, by referring to a chart or map, can determine on which side of the desired course he is proceeding. In the system in most general use, the so-called A-N system, signals in the adjacent quadrant are pulse-coded to represent the Morse code letters A and N which are complementary so that, when on the true course, the pulses of one coded signal fill in the gaps of the other coded signal and the pilot hears in his receiver a continuous tone of constant amplitude.

However, the range systems in use have involved the continuous use of headphones by the pilot, which tends to .distract him from his many other duties and is subject to the defects or limitations on the sensitivity of the pilot's hearing. It is desirable to provide a coded range-signal system which is not dependent upon the continuous use of headphones for audible reception.

It is an object of the invention, therefore, to provide a new and improved coded range-signal responsive system which avoids the continuous audible reception of a coded range signal.

It is another object of the invention to provide a new and improved coded range-signal responsive system by means of which there may be obtained an electrical or mechanical effect or signal representative of the quadrant in which the aircraft is flying, which effect may be utilized for visual indication or for navigational control purposes.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings while its scope will bepointed out in the appended claims.

In accordance with the invention, in a codedpulse ranging system, an aircraft range-responsive system comprises means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses occurring only at edges of the pulses of the received range signal, and means responsive to the time separation of the derived pulses for developing an effect representative of the quadrant in which the aircraft is flying.

Further in accordancewith the invention, in a system of the type described, the means for deriving the pulse wave from the received range signal comprises means for differentiating the detected range signal to develop a derived pulse wave and means for rectifying such derived pulse wave, the time-responsive means being responsive to the time separation of the pulses of such rectified wave.

Further in accordance with one form of the invention, the means responsive to the time separation of the derived pulses comprises means for generating a contro1 pulse wave having pulses of a duration greater than the least time separation of one of the detected range signals and less than that of the other of the detected range signals, the means, for developing the quadrantrepresentative effect being means responsive jointly to the derived pulse wave and the developed control pulse wave.

In accordance with another form of the invention, the time responsive means comprises means for integrating the pulse wave derived from the detected range signal and means responsive to the peak amplitude of the integrated wave for developing the quadrant-representative effect, as described.

Further in accordance with a preferred form of the invention, the range responsive system includes also means for developing an elfect varying with the deviation of the aircraft from the junction of adjacent ranges, this effect being utilized either independently or for modifying the quadrant-representative efiect in order to derive an effect representative of the position of the aircraft in the range system.

Referring now to the drawings, Fig. 1 is a circuit diagram, partially schematic, of a complete coded range-signal responsive system embodying the invention; Fig. 2 comprises a series of curves representing operating characteristics of the system of Fig. 1 to aid in the explanation of the invention; Fig. 3 is a circuit diagram of an alternative arrangement responsive to the time separation of the derived pulse wave; Fig. 4 is a series of curves or graphs representing operating characteristics of the circuit of Fig. 3 to aid in the explanation of the invention; Fig. 5 is a circuit diagram of a modified form of the means responsive to the time separation of the derived pulses which may be utilized in the complete system of Fig. 1; while Fig. 6 is a circuit diagram, partially schematic, of a'ieatureof the-invention which maybe-incorporated in the systemsof any of Figs. 1, 3 and 5 for deriving an effect representative of the deviation ofthe aircraft from the junction of two adjacent signal ranges.

Referring now to Fig. 1 of the drawings there is represented for use in a code pulse-ranging system an aircraft range responsive system com prising means for receiving and detecting the range signals, which may be of any conventional form such as the range signalreceiver Hi connected to a receiving antenna II. The 'output terminals of the receiver 10 are connected to an amplifier tube I 2 .provided with a grid leak resistor 1.3, the anode of the tube l2 being connected to a suitable source +B through a load resistor I l. The output signal from tube I2 appearing across 'load'resistor 14 is a carrier-signal modulated by a pulsed "tone-frequency wave. This signal is applied through 'a coupling capacitor l5'to a diode rectifier 'lfi'provided with aload resistor "I 1 across which appears 'the negative half of the 'modulated signal amplified by tube 12. The output signal developed .across the load resistor I? is then applied to a low-pass filterfnetwork comprising a series .r'e'sis'tor l8 and a shunt capacitor [9 for eliminating the tone-frequency components to derive a unidirectional pulse wave.

The system also includes means for derivin a pulse wave comprisingpulses of predetermined polarity occurring :only at 'the'edges oi the pulses of the received range signals, this means preferably comprising means for differentiating the detected range signal to'developa derived 'pulse wave and means for rectifying the derived wave. The differentiating 'm'eans consists of a series capacitor and a shunt resistor 2| connected across the filter capacitor I 9, while the rectifying means consists of a diode rectifier 22 in series with a load resistor 23 connected'across theresistor 2i of the difierentiating means. The derived pulse wave developed "across the load 'resistor 23 is applied to an amplifier "tube 24 the anode of which is connected to a source +B, :as indicated, through a load resistor '25. The amplified pulse wave developed across resistor 25 "is limited or clipped by means of a-diode 26 connected thereacross and having itscathode biased positively by means of a voltage divider resistor Z'lconnected across'the source +B. I

The system also includes means responsive to the time separation of the pulses of the derived wave, that is, the rectified differentiated Wave developed across the load resistor 23 and amplified in the tube 24 for developing an effect representative of the range in which the aircraft is flying. Preferably this means includes a pulse wave generator for developing a control pulse wave consisting of pulses of a duration reater than the least time separation of one of the detected range signals and less than that of the other of the detected range signals. This pulse generator may be of any of several Well-known types there being illustrated by way of example a multivibrator 28. This multivibrator 28 includes a pair of vacuum tubes 29 and 30 having load resistors 3| and 32, respectively, and energized from a suitable source +3. The two tubes are cross coupled, that is, the control electrode of tube 29 is coupled to the anode of tube 30 by means of a coupling capacitor 33 while the control electrode of tube 30 is coupled to the anode of tube 29 through a coupling capacitor 34. The input electrode of the tube 29 is synchronized by the amplified derived pulse wave developed across resistor 25 by means of a-circuit including a couplingcapacitor 35and=a variable grid re: sistor 36, which is provided for adjustment of th'e width of the pulses generated by the multi vibrator 28.

, Thetime -responsive means also includes means I responsive jointly to the derived pulse Wave and :representative efiect.

the control pulse wave for developing the range This last named means comprises a vacuum tube key or amplifier 31 for repeating 'tl'iederived pulse waves which are apcathode is biased positively from a resistor .4'4

forming 'with a resistor '45 a voltage "divider connected acrossthesource +3.

The effectrepresentative of therange in which the aircraft is'fiyingmaybe 'a signalgeither electrical or mechanical. "In the system described, an 'e1ectrica1 signal i's'developed'in'the'output'circuit of the key 3'! wheneverthe derived pulses from the load resistor "25 "a'ndthe keying pulses from the multivibrator28are simultaneouslyapplied "to its inputelectrode; thatis, only" when the aircraft is in one or the predetermined signal ranges. The system also includes 'a visual indicator responsive to this signal and comprising 1 a two-position relay '46 having normallyopenand normally closed contacts 46a and l fihrespectively, and an energizing winding 46c excited by the electrical Sigh-9:1 develo ed by'the'key 31. The exciting circuit for the winding 460 includes a diode rectifier "47 coupled across load resistor 43 by means or a couplihgcapac'itorifl andprovid'ed with a load circuit comprising aparallel-"conn'ec'ted resistor 49 and capacitor 50, this load "circuit being connected to the control electrode of "a vacuum tube amplifier 5i 'having'an anode circuit including the winding 45c and energized fromi'a suitablesour'ce +13.

The visual indicator ais'o includes means controlled by the relay 46 for developing distinctive e fie'cts individually representative 'of each of the ranges when the aircraft is fiyi'ngtherein. Specifically, this means "comprises a two-position, zero-center indicator or meter 52 provided with an indicator or 'point'er52a actuated by the windings 52b, 52ct'o "one side or the other of its zero position, which is 'indicate'dby the representation of a beam 52d on "the face of the meter. The windings 52b and 52b are 's'eledtively energized by means of the contacts "46a and "5b, respectively, or vice verse, by means of "a two-pole double throw switch 53 and a suitable current source,

. such as a battery '54. The indicatorsd 'includes'a mechanism 55, represented "in dashed lines, withv a pair of range indicators A-N and N-A asso-' ciated with the windows 52 and 52g, respectively, in the face of the meter. The linkage 55 is also connected to the double throw switch 53 for simultaneous operation of this switch and the,

range indicators N-A and A-N.

Coming now to the operation of the range-signal responsive system of Fig. 1, range signals are picked up on the antenna l i, received in the unit It), amplified in the amplifier I2 and detected in the diode detector Hi all in a conventional manner. The modulation envelopes of the detected range signals appearing at point A of the output circuit of detector is are represented by curves a and a of Fig. 2, assuming that the plane is operating in the conventional A-N range system now in current use. Curves a and a represent the Morse code signals A and N, respectively, it being seen that the pulse curve a, fit into the intervals of curve a; that is, the two pulse signals are complementary. Each of curves at and 11' represents the modulation envelope of the pulsemodulated tone signal resulting from the detection of the received tone signal in the detector It. The tone modulation component, usually 1020 cycles, is substantially removed by the filter circuit comprising the series resistor I8 and shunt capacitor I9, resulting in a unidirectional signal of the shape of curve a or curve a, depending upon the range in which the aircraft is flyi s.

The detected and filtered signal is then differentiated by the circuit comprising the series capacitor 2i! and the shunt resistor 2| resulting in the derived pulse wave, curve b or curve I) of Fig. 2, comprising pulses occurring at the leading and trailing edges of the pulses of the wave of curve a or curve a, these derived pulses having a very narrow but substantially constant width; that is, a duration substantially constant but much less than that of any of the range signal pulses. The derived pulse wave of curve b or curve 1) appears :at point B of the difierentiating circuit 20, 2! and is impressed upon the diode rectifier 22 which develops across its load resistor 23, that is, at

point C, a pulse wave of the form of either cure c or curve C of Fig. 2, representing the pulse wave utilized to discriminate between the detected range signals on the basis of the time separation of their respective pulses. The pulse wave of curve c or curve is amplified in tube 24 and clipped or limited in the diode rectifier 26 approximately to the value of the unidirectional potential appearing across the portion of the voltage divider 2i utilized to bias the cathode of the diode 26. This clipping or limiting action is effective to stabilize the resultant pulses at a substantially constant amplitude level irrespective of variations in intensity of the received signal.

The derived pulse wave of curve 0 or curve 0 of Fig. 2 is utilized to synchronize the multivibrator 26, which is an entirely conventional circuit the detailed operation of which need not be explained. Briefly, due to the cross coupling between the tubes 29 and 30 of the multivibrator, they turn each other on and off alternately, generating a pulse wave the duration and separation of the pulses of which are dependent primarily upon the time constants of the resistancecapacitance circuits connected to the grids of the tubes. By adjusting the resistor 36, the periodicity of self-oscillation of the multivibrator 28 can be brought to a value only slightly greater than that of the pulses of curve 0 or curve c so h he m br or i sy chr n zed Pric pulses. There is thus developed across the resistor 42 at point D of the multivibirator 28 a pulse wave of the form of curve d of Fig. 2 and this pulse waveis applied positively through the coupling circuit 40, dl to the control electrode of the repeater 31. It will be noted that the pulse wave of curve dis somewhat delayed with respect to its synchronizing pulse wave, curve 0; this delay may be obtained by selection of appropriate circuit constants of the coupling circuits or those of the multivibrator 28.

The cathode of the key 31 is normally positively biased by the portion M of the voltage divider 44, 5 and the value of this bias is so selected in relation to the amplitude of the pulses derived from point D that the repeater 31 is at or near its cut-off point duringthe occurrence of the pulses but is biased substantially below cut-off in the intervals therebetween. The limited pulses, curve 0 or curve 0' appearing at the output circuit of the amplifier 24 are also applied to the control electrode of key 3'! through the unidirectionally conductive device 38 and an isolating resistor 39. By virtue of the biasing of the key 31, it is effective to repeat only such of the pulses of the pulse Waves of curve 0 or curve 0 as occur simultaneously with the pulses of curve d.

From Fig. 2 it is evident that the spacing of the pulses of curve 0, representing the A signal, is such that the second pulse of each pair, the first of which initiates a cycle of the multivibrator 28, occurs during the suceedin-g pulse of curve d generated thereby so that this second pulse is repeated and amplified by the key 31. This repeated pulse is applied by a coupling capacitor 48 to the diode rectifier 41 having a shunt load circuit 49, 58 having a longtime constant efiective to develop a unidirectional signal approximately equal to the peak value of the repeated pulses. The time constant of the circuit 49, 50 is also preferably sufliciently long to maintain this unidirectional signal during the identification-signal interval between successive transmissions of range signals, which usually is about 7 seconds. The unidirectional signal developed across the load circuit 49, 50 from the pulses of curve 0 is applied as a negative bias to amplifier 5| the output circuit of which includes winding 460 of the relay 46 so that, when A-quadrant signals are beingreceived, relay 46 is de-energized.

On the other hand, it will be seen from the curves of Fig. 2 that none of the pulses of curve 0' corresonding to the N-quadrant signals, occur during the generated pulses of curve d so that no output signal is developed by the key 31, no

negative bias is developed and applied to amplifier 5i, and relay 46 is energized. That is, the control pulse wave of curve d comprises pulses of a duration greater than the least time separation of the detected A-quadrant signals and less than that of the detected N-quadrant signals. The key 3! comprises means responsive jointly to the derived pulse wave of curve 0 or curve 0 and the control pulse wave of curve 0, for developing an electrical signal only during the reception of the A-quadrant signals.

As stated above, the electrical signal developed by the key 31 and the rectifier M is applied as a negative bias to the amplifier 5! to control the excitation of the two-position relay 46. When the relay 46 is in a de-energized position, corresponding to the reception of A-quadrant signals as illustrated, and with the two-position switch 5 3 also in the position illustrated, it will be seen that the winding 520 of the zero-center meter 52 is energized from the battery 53. Such.

position of the switch 53 corresponds to the posi-- tion of indicators N-A and A-N ofthe meter 52 as. shown so that-the symbols A and N appear in the windows 52 and 52g, respectively, while the pointer 52a is deflected to the-left adjacent the window 52f. Thus the. meter '2indicates that the aircraft is flying in the A-quadrant. It will be understood that, in operating the system, the pilot will refer tov his range chart to determine the relative location of the A and Nquadrants for the particular direction in which he is approaching the. range beacon. He. will then'operate the knob or lever 52c to. shift the indicators A-N and N-A and to throwthe switch 53.into. the positioncorresponding thereto so that, under-all conditions, the. position ofthe. indicator with respectto; the A or Niside. ot'the meter will be .correct;

From the. foregoing. explanation it will be apparentthat, upon receptionof an N-quadrant signal, the pulses ofcurve of are not repeated in key BLandno. unidirectional bias is developed acrossthe load circuit 49,; 50.so thatthe relay 46 isenergized by the amplifier 53 to close. its contact 4.6a. thus energizing the winding 52b of the meter 52 ;Which deflects the, pointer 52a. to the opposite side: to indicate. to the pilot thathe is flying in the N-quadrant.

In Fig- 3 there is represented, a modification: of a p rtion, ofthe range-r sponsive system of Fig 1 embodying; different means responsive tothe time separation, of the derived pulses, The circuit prior to the point Am the channel maybe identical to that of. Fig. land thereforeis omitted forthe sake of simplicity. The detected pulse wave; curve. a or curve a: of Fig. 2, is impressed upon the control, electrode of. vacuum tube amplifier 68 having an anode circuit including a loadresistor BI and afilter capacitor 63.. and energized from a suitable source. +B;. its controlelectrode. being provided with a grid. leak resistor 62.v The filtered pulse wave. developed across resistor 61 is then applied to a differentiating circuit comprising a series capacitor Mand shunt resistor 65, the diflerentiatedpulse, represented by .curve 1). or curve I) of Fig. 4, being developed acrossthe resistor $5. b orcurveb. appearing at the-point B is applied to the input'electrode of avapor-electric discharge tube: G'Efiwhich may be of the -Thyratron type including in its output circuit a self-quenching or suppressing circuit comprising an anode load resistor 67 and shunt capacitor 68. The constants of the elements El and- 68-aresuch' that thecurrent through the tube 66 extinguishes itself after a briefpulse, as is wellunderstood in the art. The tube 65- is provided with cathode loadresistors 69, 79, these resistors forming with a resistor a voltage divider across-the source +13, as indicated, for normally biasing the tube 66 to a non-conductive state.

The range signal responsive system of Fig. 3 alsoincludes means for integrating the derived wave comprising a rectifier including a load circuit having a time constant substantially longer than the least time separation of the detected A,-range signals and substantially less than that of the detected N-range signals. This means comprises a rectifier 73 provided with a load circuit including resistors 14, and, T6 in series, the resistor 15 being shunted by a capacitor 11 and forming therewith a, time constant circuit as described. The amplified pulses'of curve 0 or curve 0' appearing across the loadcircuitGB.

The pulse wave. of curve.

a 10- are applied to. the rectifier 13; througha: coupling; capacitor l2.

The system of Fig. 3 also. includes means. re.-- sponsive. to the peak amplitude of the integrated wave for-developing anaeff'ect representative of the range in which the-aircraftisflying, Specifi: cally, the integratedsignal :appearing across the time constant-circuit I5, 11 israpplied toya diode. peakrectifier 18Lhaving a. load circuitzincluding;- resistors 19 and 80 in series, the resistor 19 being shunted by' a capacitor. 8| through a resistor 82;. the time-constant circuit 19,: 8|,. 82 having a time constant-of at least several seconds. The diode. 18 is biased by the resistor 80 .forming with a. resistor: 83 a voltage divider circuit connected, across thesource +B so that the. diode l8irecti-i fies only applied pulses of. greater: than a. predetermined amplitude. The. integrated, peak. rectified pulses-appearing across load circuit 19, 83 are applied to an" amplifier B4. normallybiased; at or beyond cut-off 'bymeans of a voltagedivider comprising resistors 85, 38 connected across the source --[-B. The output circuit of amplifier 84: includesthe windingof relay 46.

The operation of the system of Fig. 3 may be explainedwith reference to the curves of Fig. 4. The detected, filtered and di-fierentiated pulse Wave-of curve b or curve b developed at the point B in amanner similar to the arrangement of- Fig. l'are utilized to key or trigger the vapor-electric: tube 66 and its relaxation circuit so that thereappear in its cathodeload circuit 69,10 amplified positive-pulses only of substantially the same wave form and duration as thepulses of curve I) orcurve I). These pulses are applied to the rectifier 73 having in its load circuit the time constant circuit l5, ll the value of the time constant of which issuch that the capacitor 71 is charged by successive pulses but is substantially discharged in the interval corresponding to-theleast time separation lof the positive pulses of curve-b, corresponding to N-quadrant signals, the capacitorvoltage-being represented by curve gof Fig; 4. As a result, the maximum value ot the signal developed across-the load circuit 15, 11 does not exceed the value at, representing the delay bias, impressed onthe cathode of the diode 18 fromvoltage divider 8H, 83. Therefore, when N-quadrant signals are being received, no signals are rectified by the diode 18, no signal is im-- pressed uponthe vacuum tube amplifier 84, and the-relay dfi-remainsde-energizedso that themetenSZ '01- Fig. 1 indicates that-the aircraft is operating in the N-quadrant.

However, the time constant ofthe circuit 15, TI is such-that the capacitor Tl discharges only to the level 1 of Fig. Aduring the interval corresponding to the least time separation. of the derived pulses of curve -b, corresponding to the- A-quadrantsignals- As a result, upon the occurrence'of the second positive pulse of curve'b of each" pair-ofjadjacent pulses, the condenser 11 is-given' an-additionalincrement oi-charge which carries as potential substantially abovethe valveof the-delay bias w, as represented by curvea, Fig. 4: The portions of the pulses of curve ainexcessof the delay bias m are rectified in the peak-rectifier 18; The load circuit 1-9, 8|, 82 of this rectifier has a long time-constant chargingcircuit 81,- 82 sothat it-is substantially unresponsive; to the identificationsignals transmitted-'during the interval between successive transmissions of range signals. In addition, it has aiconventional long time-constant discharg- -ing circuit -19; 8|; 82 "to enableit to function as" a peak rectifier, deriving from the intermittent pulses of curve 6 in excess of the delay bias :1: a continuous unidirectional potential for application to the amplifier 84 and relay 46. Thus, as in the arrangement of Fig. 1, the relay 46 is either energized or de-energized in accordance with whether the aircraft is operating in the A- range or the N-range and correspondingly controls the zero-center meter 52 to provide a visual indication thereof. However, it is to be noted that, in this modification of the invention, the operation of relay 46 is reversed with respect to that of the Fig. 1 system, being energized upon the reception of A-range signals and de-energized upon the reception of N-range signals, so that the connections to the meter 52 are to be reversed with respect to those of Fig. 1.

Referring now to Fig. 5, there is represented a modification of a portion of the system of Fig. 1 for positively developing an electrical signal upon the reception of either A-quadrant or N -quadrant range signals. In this case the detected filtered and differentiated pulse wave of curve b or curve I) of Fig. 2 developed at point B in the channel of Fig. 1 is applied to the control electrode of a vacuum tube amplifier 90 having a cathode load resistor 91 which, with an adjustable resistor 92, constitutes a voltage divider connected across the source +B which also supplies space current to the tube 90. The amplified pulse wave corresponding to the pulses of curve I) or curve I) of Fig. 2 is applied to the control grid of a vacuum tube 94 connected as a conventional blocking oscillator; that is, its control electrode circuit includes a time-constant circuit comprising a resistor 95 and a capacitor 96 in parallel while the anode circuit is regeneratively coupled to the control electrode circuit through a feed-back transformer 91. The anode of the tube 94 is energized from a source +B while its screen electrode is similarly energized through a dropping resistor 98. The time-constant circuit 95, 96 is also coupled to point B through a filter circuit comprisin series resistors 99, I and a shunt capacitor WI. The blocking oscillator described constitutes means for generating a control pulse wave which may be used interchangeably with the multivibrator 28 of Fig. 1, the circuit constants being so selected that the generated pulses are of a duration greater than the least time separation of the detected A-range signals and less than that of the detected N-range signals.

The pulse wave developed by the blocking oscillator at the point D is somewhat delayed, as indicated in Fig. 2, by the circuit constants of the blocking oscillator and its coupling circuit. This pulse wave, curve d, is applied through a coupling capacitor I02 and a coupling capacitor I04 to a repeater means such as the vacuum tube repeater I06. The repeater I06 is provided with a control electrode circuit for keying the repeater with the generated pulse wave of curve 11 comprising the coupling condenser I04 and adjustable grid resistor I08 and a grid biasing circuit comprising a grid leak resistor I 09 and shunt condenser H0. The repeater I06 is also provided with a cathode load resistor III which, with a resistor H2, comprise a voltage divider circuit across the source +3.

The pulse wave of the blocking oscillator 94 is also applied to a second repeater 06 through a delay network H03, which is effective to delay by an amount not less than the least time separation of the detector A range signals. The

repeater I06 and its associated circuits are, with the exception of the additional delay network I03, identical to those of the repeater I06, corresponding elements being identified by the same reference numerals primed, so that description thereof need not be repeated. The point B is also coupled to the repeaters I06 and I05 through coupling condensers Iota and IBM, respectively.

The operation of the system of Fig. 5 will be apparent from the foregoing description in conjunction with the explanation of the operation of the preceding modifications. Briefly, the detected, filtered, and differentiated pulses of curve b or curve b are repeated by the amplifier and applied with the same polarity from its cathode load resistor 9| through the coupling capacitor N32 to synchronize the blocking oscillator 90. The oscillator 94 generates a pulse wave, curve d, Fig. 2, similar to that generated by the multivibrator 28 of the system of ,Fig. 1 and slightly delayed with respect to the synchronizing pulse wave, curve b or curve 12. This pulse wave is applied to the control electrode of the repeater tube I06 to which is also applied the derived pulse wave of curve I) or curve I) from point B through capacitor E0011. The repeater I 06 therefore operates in a manner analogous to the repeater 31 of Fig. 1, energizing the relay 46 only uponthe reception of A-quadrant signals. At the same time the pulse wave, curve d, Fig. 2, is delayed by the network I03 to develop the pulse wave, curve c, Fig. 2. The amount of the delay is greater than the separation of the closest positive pulses of curve 2) (same as curve 0) derived from the A-quadrant signals so that the repeater Hi6 does not respond to the A-quadrant signals supplied to its control electrode through the coupling capacitor 15a. However, the delay of the pulse wave curve 6 is less than the least time separation of the N-quadrant signals so that the repeater I06 is keyed to respond to the next successive positive pulse of curve b (same as curve 0') derived from the N-quadrant signals and, therefore, is effective to energize its associated relay 46 when the aircraft is operating in the N-quadrant. The relays 46 and 46' may individually control the excitation of the windings 52b, 520 of the indicator of the system of Fig. 1 through a reversing switch 53 in substitution for the two-position relay 46 of Fig. 1.

In each of the systems of Figs. 1, 3 and 5 a mechanical or electrical signal is developed which gives an indication only of the quadrant in which the aircraft is flying but does not give an indication of the degree of deviation of the aircraft from the desired course, which is usually the junction of the adjacent quadrants and appears in the form of a narrow-angle beam of steady tone. In Fig. 6 is illustrated a circuit which may be added to the arrangement of any of Figs. 1, 3 and 5, but has been separated therefrom for the sake of simplicity, which circuit includes means for developing an efiect varying with the deviation of the aircraft from'the junction of adjacent quadrants. The derived pulse wave of curve 0 or curve 0' of Fig. 2 developed at the point C, Fig. l, is applied to an A-N sorter circuit I20 which, for example, may be comprised of the amplifier 24 and its associated circuits, the multivibrator 28, the repeater 31 and its associated circuits, and the amplifier 5| of Fig. l. The output circuit of the unit I20 includes the two-position relay 46 which maybe identical to that of Fig. 1. The contactslfia ment of-Fig; 1.

---,and 46b of relay 46 are connected :to the windings-52b and-52c of "the indicator-or meter '52 through a reversing switch53-asin therarrange- In this instance, however, .the energization of the windings of the :meter .52 is obtained from means for deriving an effect vary- ,ing with the effective modulation-of the sum-:of

the received range signals, which is "representative ,of the deviation of the aircraft from the junction of adjacent quadrants. This means comprisesa combining amplifier tube .I-2I, pref- :erably of the heptode type, as illustrated. =,'Io .the innermost control electrode are applied the .:unidire ctional pulses of curve a or curve a through .a long time-constant circuit comprising series resistors I22, I23 and shunt capacitors I24 and I.25-so that this grid operatesasa peak ,grid rectifierv to control the amplification .of the tube I2I in accordance with the peak intensity of the signals of curve a orcurve-ia.

The -,pulse .wave of curve aor curves is also applied .to the second input gridof the amplifier I2I through afilter-circuit comprising series-resistors IZBand. I-Z'I andshunt capacitors I28 and .129 for filtering out the audio-frequencyucomponent, this control electrode being .rprovided with a, grid resistor 130. The screen and anode .of ,the tube [21 are energized through resistors .I3I.,and I32, respectively, iroma-suitable source v I-B. The output .of amplifier I2-I appearing :acrossload resistor I32 .is applied through a cou- -;pling capacitor 133 and voltage divider resistor 134 to -a full-wave bridge rectifier circuit 135 which maybe of any type but is preferably of the-copper-oxide contact type, as indicated. The

unidirectional output circuit of the rectifier bridge I35 is connected :in placeof the battery54 .of the-systemof Fig. 1 througha ,long time-constant filter circuit comprising a series resistor I31 ,and shunt condensers I36 and .I 38,- selectively to energize the windings 521), 52.0 of the indicator 52inaccordance with the relative positions of the relay. and the reversing switch .53.

The operation-of the system of Fig. 6 for! developing an electrical signal representative of the -quadrant-in which the aircraft is flyingcomprisingthe unit I20, the relay v46, thereversing switch 53 and the indicator 52 .is (similar to that of the system-ofFig 1. In accordance with-the rarrangemen-t of ,Fig. '6, however, this quadrant effect is; modified with the'deviation-effect; that is, with an effect representative .of the deviation of the aircraft from the desired course as measured :by the eiTective modulation of the sum of ,the received vquadrant signals to :derive an effect representative ,of the position of the aircraftrin -d;he;;range system. This modifying-effect ,is derived, byJthe1comhmingamplifier 'I2I to the .sec- .ondinput grid of which .is-applied the sumaof .the -.q.uadrant signals. of. curves at and a of Ei 2.

"If "the aircraft-is exactly (on course, the two range signals :are receivedwith equal amplitudes, ;the pulses of one ofxthesig-nals exactlyfillthegaps ,of the other signal, and the tone :signal appears constant, thatiis, atcontinuous-4100 %qmodulation. If, however, the aircraftis tonne .sidev or.the other of the-desired course, either .the A-quadrant signal or athei-N-quadrant signal willpredominateand thesum voff-the two signals will "have "an apparent orjeffective modulation ,at the pulse rate. At .thesame time, in order *to compensate for r-variations in the peak intensity .of the range signals in accordance withthie distance of the 'aincraftfrom their source, thepeak rectifier'comprisingsthe inner grid of the tube v=I-2I .andzthe 'timewonstant'.--cir.cuit 1122, I223, I24, I25iactsas an automatic amplification control :.to. maintain :the output-of the amplifier I21 substantially independent of variations in input intensity. The

resultant signal output of the amplifier I, therefore, consists of a pulse signal of an amplitude dependent "upon the eifective percentage modulation 10f the rsum of the range signals and this pulse signal is 'rectified-bythe rectifier I35 to provide a source of excitation for .the windings of the indicator 52. Therefore, the direction of deflection -of thev meter 52 is determined by the quadrant in which the aircraft is flying while the extent of :its deflection is determined by the deviation from :the' beameourse, that is, by the effective modulation of the sum of the received quadrant signals. In other words, the meter 52 develops an effect, :that is, a deflection, representative of "the position of the aircra'ft-inthe range system. "Thus, the indication of the indicator '52 constitutes a visual signal varying in polarity withthe quadrant in which the-aircraft is operating, specifically its mechanical deflection oneither side of the zero position, and varying in amount in accordance with the deviation of the aircraft from the junction ef the adjacent quadrants.

While the invention has been illustrated and described in a system for obtaining a Visual indication of the relative position of the aircraft in the ranging system,-'it will be apparent to those skilled in the art that the electrical signal derived to determine such position'may be utilized for measuring, indicating'andcontrol purposes generally.

While there'have-been described what are at present consideredto be the preferred embodiments of the invention, 'it will be apparent to those skilled in the art that various changes and modifications may be -rnade therein without departing from the spirit or scope of the invention.

I claim:

1. In a coded-pulse ranging system, anaircraft range-responsive"system comprising, means for receiving and detecting-the range signals, means for receiving and detecting the range signals,

means for deriving a pulse wave comprising pulses of substantially constant duration occurring synchronously With..the pulses of the received range signal, means governed by said derived pulses for generating sustained control pulsesflof .pre determ'ined durations in response .tocertainof said derived-pulses, and aperiodic -.meansresponsive to the coincidence of others of said derived pulses with said controlpulses depending upon the time separation of said derived pulses for developing a continuous effect representative ofv the quadrant in which said aircraft is flying.

3. In-acoded-pulse ranging system, an aircraft range-responsive system comprising, 'means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses of a duration substantially constant and much less than that of any of the range-signal pulses and occurring synchronously with the pulses of the received range signal, means governed by said derived pulses for generating sustained control pulses of predetermined durations in response to certain of said derived pulses, and aperiodic means responsive to the coincidence of others of said derived pulses with said control pulses depending upon the time separation of said derived pulses for developing a continuous-effect representative of the quadrant in which said aircraft is flying.

4. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses of predetermined polarity occurring at the edges of the pulses of the received range signal, means governed by said derived pulses for generating sustained control pulses of predetermined durations in response to certain of said derived pulses, and aperiodic means responsive to the coincidence of others of said derived pulses with said control pulses depending upon the time separation of said derived pulses for developing a continuous effect representative of the quadrant in which said aircraft is flying.

5. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses occurring only at the leading edges of the pulses of the received range signal, means gov erned by said derived pulses for generating sustained control pulses of predetermined durations in response to certain of said derived pulses, and aperiodic means responsive to the coincidence of others of said derived pulses with said control pulses depending upon the time separation of said derived pulses for developing a continuous effect representative of the quadrant in which said aircraft is flying.

6. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses of substantially constant duration and of predetermined polarity occurring only at the edges of the pulses of the received range signal, means governed by said derived pulses for generating sustained control pulses of predetermined durations in response to certain of said derived pulses,

and aperiodic means responsive to the coincidence of others of said derived pulses with said control pulses depending upon the time separation of said derived pulses for developing a continuous effect representative of the quadrant in which said aircraft is flying.

7. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for differentiating the detected signal to develop a derived pulse wave, means governed by said derived pulses for generating sustai'nedcontrol pulses of predetermined durations in response to certain of said derived pulses, and aperiodic means responsive to the coincidence of others of said derived pulseswith said control pulses depending upon the time separation of said derived pulses for deriving a continuous effect representative of the quadrant in which said aircraft is flying. Y

8. In a coded-pulse-ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for differentiating the detected signal to develop a derived pulse wave, means for rectifying said derived pulse wave, means governed by the pulses of said rectified wave for generating sustained control pulses of predetermined durations in response to certain of such rectified pulses, and aperiodic means responsive to the coincidence of others of such rectified pulses with said control pulses depending upon the time separation of the pulses of said rectified wave for deriving a continuous effect representative of the quadrant in which said aircraft is flying.

9. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses occurring only at edges of the pulses of the received range signal, means governed b said derived pulses for generating sustained control pulses of predetermined durations in response to certain of said derived pulses, and aperiodic means for discriminating between the detected range signals on the basis of coincidence or lack of coincidence between others of said derived pulses and said control pulses according to the time separ-ation'of the respective derived pulses for developing a continuous effect representative of the quadrant in which said aircraft is flying.

10. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses occurring only at edges of the pulses of the received range signal, means for generating a control pulse wave having pulses of a duration greater than the least time separation of one of the detected range signals and less than that of the other of the detected range signals, and means responsive jointly to said derived pulse wave and said control pulse wave for developing an effect representative of the quadrant in which said aircraft is flying.

11. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses occurring only at edges of the pulses of the received range signal, means for generating a control pulse wave having pulses of a duration greater than the least time separation of one of the detected range signals and less than that of the other of the detected range signals, keying means for keying said derived pulse waves, a circuit for keying said keying means with said generated pulse wave, and means controlled by said keying means for developing an effect representative of the quadrant in which said aircraft is flying.

12. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means 'for receiving and detecting the range signals,

means for deriving a pulse wave comprising pulses occurring only at edges of the pulses of the received range signal, means for generatin a control pulse wave having pulses of a duration greater than the least time separation of one of the detected range signals and less than that of the other of the detected range signals, means for delaying said generated wave by an amount not less than the least time separation of said one of said detected range signals, a pair of keying means for keying said derived pulse waves, a circuit for keying one of said keying means with l said generated Wave, fa circuit. for key-ingthe other pr said keying. means with .said delayed wave,1and means controlled by said keying means for developingan effect representative of the'quadrant in which said aircraft :isfiying.

13. .In a coded-pulse ranging system, an'air- :cr-aft range-responsive.system comprising, means for receiving and detecting the range signals, m'eans for deriving a pulse wave comprising pulses occurring only at corresponding edges of the pulses of the received range signal, means for integrating the derived pulse wave, and means responsive to the peak amplitude ofisaid integrated wave When the derived pulses havea predetermined time separation for developing .an "effect representative of the quadrant in which said aircraft is flying.

14:. In a coded-pulse ranging system, an 'aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses occurring-only at corresponding edges of the pulses of the received range signal, means for integrating the derived-pulse wave comprising a rectifier including a load circuit having a time constant substantially longer than the least time separation of one of the detected range signals and substantially less than that of the other of the detected range signals, and a peak rectifier including a load circuit having a time constant substantially greater than the longest interval between successive range signals for developing an effect representative of the quadrant in which said aircraft is flying when said detected range signals have a predetermined time separation. I

15. "In a coded-pulse ranging system, an aircraft range-responsivesystem comprising, means for receiving and detecting the range signals, means for deriving a pulse Wave comprising pulses occurring only at edges of the pulses of the re- .ceived range signal, aperiodic means responsive to the time separation of said derived pulses of a? predetermined polarity for developing a continuous efiect representative of the quadrant in which said aircraft is flying, and means for developing an eflect varying with the deviation of the aircraft from the junction of adjacent quadrants.

16. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse Wave comprising pulses occurring only at edges of the pulses of the received range signal, means responsive to the time separation of said derived pulses for developing an effect representative of the quadrant in which .saidaircraft flying, and means for deriving'an effect varying with the efiective modulation of the .sum of the received range signals and representative of the deviation of the aircraft from the junction of adjacent quadrants.

1'7. In a coded-pulse ranging system,.an .aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprisingpulses occurring only at edges of the pulses of the received range signal, means responsive to the time separation of said derived pulses for developing an effect-representative of the quadrant in which said aircraft is flying-means for developing an effect varying with the deviation of the aircraft from the junction of adjacent quadrants and :means for modifying the (quadrant effect with the deviationeffectito:derive an effect representative'of the position of the aircraft in the range system.

18. In a coded-ipulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving-a pulse Wave comprising pulses occurring only at edges of the pulses of thereceived range'signal, means responsive to the time separation of said derived pulses for developing an effect respresentative of the quadrant in-which said aircraft is flying, means for deriving an effect varying with the efifective modulation of the sum of the received ran e signals, and means for modifying the quadrant effect with the modulation effect to derive an effect representative of the position of the aircraft in the range system.

19. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse Wave comprising pulses occurring only at edges of the pulses of the received range signal, means governed by said derived pulses for generating'sustained control pulses for predetermined durations in response to certain of said derived pulses, and aperiodic means'responsiveto the'coincidence of others of said derived pulses with said control pulses depending upon thetime separation of said derived pulses for developinga continuous electrical signal representative of the quadrant in which said aircraft is flying.

20. Ina coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave com-prising pulses occurring only at edges of the pulses of the received range signal, means governed by said derived pulses for generating sustained control pulses of predetermined durations in response to certain of said derived pulses, and aperiodic means responsive to the coincidence of others of said derived pulses with said control pulses depending upon the time separation of said derived pulses for developing a continuous signal varying in polarity in accordance with the quadrant in which said aircraft is flying.

21. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses occurring only atedges of the pulses of the received range signal, means governed by said derived pulses for generating sustained control pulses of predetermined durations in response to certain of said derived pulses, aperiodic means responsive to the coincidence of others of said derived pulses with said control pulses depending upon the time separation of said derived pulses for developing a continuous electrical signal representative of the quadrant in which said aircraft is flying, and a visual indicator responsive to saidsignal.

v22. In a coded-pulse ranging system, an aircraft, range-responsive system comprising, means for receiving and detecting the range signals,

means for deriving a pulse wave comprising pulses occurring only at edges of the pulses of the receiVedrange-signaI, means responsive to the time separation'of said derived pulses for developing an electrical signal only when said aircraft is flying in one of the quadrants, a twoposition' relay actuated by said signal, and means controlled by said relay'for developing distinctive effects individuallyrepresentative of-each of the quadrants when said aircraft is flying therein.

23. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses occurring only at edges of the pulses of the received range signal, means responsive to the time separation of said derived pulses for developing an electrical signal only when said aircraft is flying in one of the quadrants, a two-position relay actuated by said signal, and a two-position indicator controlled by said relay and including manually operable means for controlling its electrical connections in accordance with the direction from which the aircraft is approaching the source of range signals, the position of the indicator being representative of the quadrant in which the aircraft is flying.

24. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse Wave comprising pulses occurring only at edges of the pulses of the received range signal, and aperiodic means responsive to the time separation of said derived pulses of a predetermined polarity for developing a continuous signal varying in polarity in accordance with the quadrant in which said aircraft is flying and varying in magnitude in accordance with the deviation of the aircraft from the junction of adjacent quadrants.

25. In a coded-pulse ranging system, an aircraft range-responsive system comprising, means for receiving and detecting the range signals, means for deriving a pulse wave comprising pulses occurring only at edges of the pulses of the received range signal, a zero-center meter responsive to the time separation of said derived pulses and deflectable in either sense in accordance with the quadrant in which said aircraft is flying, and aperiodic means responsive to the devi-ation of the aircraft from the junction of adjacent quadrants for determining the amount of deflection of said meter, whereby said meter indicates the position of said aircraft in said range system.

WILLIAM CULLEN MOORE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,157,677 Runge May 9, 1939 2,198,445 Wesselink Apr. 23, 1940 2,271,534 Bailey Feb. 3, 1942 2,290,974 Kramar July 28, 1942 

